by definition (courtecy of Dictionary.com)

car
4-wheeled motor vehicle

Motorcycle
A two-wheeled motor vehicle resembling a heavy bicycle, sometimes having two saddles and a sidecar with a third wheel.

Bicycle
A vehicle consisting of a light frame mounted on two wire-spoked wheels one behind the other and having a seat, handlebars for steering, brakes, and two pedals or a small motor by which it is driven.